1. Field of the Invention
The invention relates in general to superconductor wire, and more specifically to superconductor wire having microparticle superconductor filaments having improved retention of filament dimensional integrity.
2. Description of the Prior Art
U.S. Pat. No. 4,411,959, which is assigned to the same assignee as the present application, teaches a submicron-particle ductile superconductor wire wherein the submicron particles are encapsulated in a metallic tube, such as copper, and then fabricated to a fine wire in the absence of sintering or reaction annealing. Bundling and fabricating the bundle produces multifilamentary composites which retain the fluid-like properties of the unsintered, submicron particle superconductor filaments.
While multifilamentary wires constructed according to the teachings of the hereinbefore mentioned U.S. patent possess excellent mechanical and electrical properties, metallographic evaluation of the wires indicates that the original circular cross-section of the filaments in the starting product is not retained during the many fabricating steps required to produce the final product. At some point in the various processing steps, the filaments become distorted and exhibit dimensional nonuniformity, both in cross-section and lengthwise.
If the filaments could be made dimensionally more uniform, superconductor behavior could be optimized, i.e., current carrying capacity would not be reduced by excessive necking down of a filament, and local heating leading to normalization and current jumping from filament to filament would not occur due to nonuniform thickness of the nonsuperconductive matrix between filaments.